St. Thomas Aquinas maintains the existence of God based on the degree of perfection found in things of the world. According to Aquinas, God must exist based on natural things having opposing characteristics: good and bad, true or false, etc., because the existence of a comparison inherent in these natural things intuitively means there must be a maximum with which to compare them to. Aquinas states that there must be a supreme, truest, noblest, best reality or being that sets the standard for all natural beings and things that follow. His argument is based on the fact that comparative things require a superlative to make complete sense.
Aquinas maintained that God’s creations could be placed in a hierarchy of sorts, like a ladder. For example, he also stated that in order to compare the hotness of a fire, it would be required to feel the hottest fire in order to make the comparison accurately. These concepts are similar to Aristotle’s philosophies that the truest is the most real and what exists most also causes it. Aquinas phrases it “Thus substance, which is first in the genus of beings and which has essence in the truest and greatest way, is the cause of accidents, which participate in the notion of being only secondarily and in a certain sense. But this happens in a variety of ways. Since the parts of substance are matter and form, certain accidents are principally a consequence of form, and certain accidents are principally a consequence of matter.” (McGibbon.2010)
Plotinus was a Greek philosopher who proclaimed that a supreme being existed but he described God as the “transcendent one” with no division, multiplicity or distinction, existing beyond all categories of being or non-being (Stumpf.1988). According to Plotinus, being for humans is inseparably connected to objects or the infinite while the transcendent one is infinite and beyond objects as existing prior to all existents. Plotinus compares God to the Sun and the soul to the moon – a “derivative conglomeration of light from the Sun.” (Stumpf.1988). His point is that God (the Sun) could exist without any celestial body whereas the moon could not.
Plotinus maintains that God is beyond being or non-being – he is the source that existed before the world was and will go on forever with no beginning nor end as an unchangeable, immutable “One”. For Plotinus, creation was not perceived in the way most Christians view the creation. Instead, creation involved life emanating from the perfect one in a series of stages of lesser perfection. Plotinus kept this system relatively simple compared to other Neo-platonic philosophers who added hundreds of intermediate beings existing in the stages between God and current humanity (Nash, 1999).
The main difference between Plotinus and Aquinas’ definitions regarding the existence of God would be, according to Steven Kimbler, “because of a metaphysical disagreement on whether being constitutes a composition. Plotinus thinks it does, and assumes that unity is most fundamental, whereas Aquinas thinks it does not, and assumes that being is most fundamental.” (Kimbler, 2010), While both believe in God, these different conceptions result in Plotinus concluding that God is beyond being while Aquinas concludes that God is the ultimate being.
Plotinus and Aquinas’ worldview is affected because of their views regarding God in that Plotinus believes all objects and existence itself to be inferior to God. Aquinas believes all is also inferior but that the existence itself is of great importance. This leaves Plotinus to disregard all “things” or objects – even his own physical body. Aquinas’ worldview is a little more positive. Plotinus rejected Aristotle’s worldview of thought because he maintained a duality in thought: the thinker and the thought. He also claimed that thoughts were multiplicity in and of themselves (Rist1973). Aristotle’s worldview was reflected in Aquinas’ worldview as well, illustrating another difference between Plotinus and Aquinas.
Aurelius Augustinus – more commonly known as St. Augustine – was a Neo-platonic like Plotinus and Aquinas but in the Judeo-Christian vein more common to Sir Thomas Aquinas. His philosophy was one of melding the Greek philosophical traditions with the Judeo-Christian religious traditions of the Roman Catholic Church. Augustine recognized a divide between the physical and the spiritual. In Augustine’s mind, God is considered the ultimate source and “point of origin for all that comes below” and is “equated with Being, Goodness and Truth.” (Stanford 2000). Augustine’s God is an unchangeable God that unifies all that comes after and below with an ordained and rational order.
While Augustine has much in common with Platonists, he does differ in that Plotinus asserts an ultimate transcendent principle that defies all characteristics. Augustine doesn’t discuss Plotinus’ assertion but repeatedly emphasizes the soul’s relation to God, emphasizing the closeness rather than Plotinus’ emphasis on the distance between the two.